Nail apparatus melanoma is generally called nail melanoma and appears when a melanocyte present in a nail matrix cancerates. In the case of Japanese, it accounts for about 10% of nail melanomas. Recuperation from the nail apparatus melanoma is considered to be unsatisfactory because making a definite diagnosis of the disease is difficult.
A melanocyte present in a nail matrix is inactive in a normal state and produces no melanin. In some cases, the melanocyte, whether or not it cancerates, starts to produce melanin. As the nail grows, the produced melanin forms a pattern called nail apparatus melanoma. If the melanocyte is not cancerous, the nail apparatus melanoma is considered to be a benign nevus. It is considered that a pattern of the nail apparatus melanoma is usable to determine whether or not the melanocyte present in the nail matrix is cancerous.
However, visually inspecting the pattern with the use of a dermoscope and determining whether the pattern is benign or malignant needs rich experience. In addition, if it is a malignant melanoma, a biopsy is generally not beneficial to the patient. These factors make it difficult to give a definite diagnosis. Such a difficulty is a factor of hindering recuperation. Accordingly, realizing a noninvasive and objective discrimination method of nail apparatus melanoma is strongly needed by clinical sites. Also, a visualization method of visually presenting a difference between benignity and malignity is strongly needed.
To diagnose malignant melanomas except the malignant nail melanoma, various discrimination methods have been proposed based on “randomness” of the shape of an edge of a malignant melanoma. One of the known means to quantify the “randomness” of the shape is a technique of using a pseudo fractal dimension (Patent Document 1). Applying a tumor test, which uses only the pseudo fractal dimension as an index, as it is to discriminating nail apparatus melanoma hardly determines whether a given nail apparatus melanoma is malignant or benign. It is also difficult for the technique to visually present a difference between benignity and malignity.